The objective of this study was to examine the significance of difference between introverted and extroverted learners in terms of syntactic complexity (Simple Sentences [SS], Compound Sentences [CpdS], Complex Sentences [CpxS], and Compound Complex Sentences [CCS]). The data were collected from written products of 30 introverted and 30 extroverted language learners in the Faculty of Languages and Arts, Universitas Negeri Medan, Indonesia. SPPS (Version 21) was used to analyze the data. It was found that there was a significant difference between introverted and extroverted learners' written product in terms of syntactic complexity. The introverted learners wrote more SS than extroverts did. In contrast, extroverts wrote more CpdS and CCS than introverts did in their written products. On the other hand, there was no significant difference between the groups in CpxS. To sum up, language learners wrote different kinds of sentences in their written products.